If you can’t get a ~real~ Hogwarts letter, these things will do…
This greeting card, perfect for the snowy season:
Christmas at Hogwarts Greeting Card, £3.76
Etsy
This sticker, remembering one of Hermione's finest moments:
Hermione Sticker In White, £1.54
RedBubble
RedBubble
27 Perfectly Magical Gifts For The Hermione Granger In Your Life